The present invention relates to a method for finishing a surface of a work by electrolytic machining, and more particularly to a method for finishing the surface to a lustrous surface at a high speed.
Japanese Patent Applications Laid-Open 61-71921 and 60-44228 disclose electrolytic machines. In the machine, liquid electrolyte such as sodium nitrate solution or sodium chloride solution is continuously passed between an electrode and a work at a high speed during machining, so that residual products such as particles of eroded metal from the work, hydrogen gas, and others are discharged from the gap between the electrode and the work.
However, in the case of the work having a complicated three-dimensional shaped recess, it is impossible to pass the liquid electrolyte through the gap having a complicated shape at a constant speed. The accuracy of the product is greatly influenced by the irregularities in the electrolyte flow. In addition, the concentration of the electrolyte at an outlet of an electrolyte tank is different from the concentration at an inlet, even if the pressure of the liquid is increased. Therefore, the machining condition dependent on the concentration of the electrolyte between the electrode and the work changes with machining position. As a result it is difficult to finish the work with accuracy. Further, in order to get a product having a high quality, it is necessary to control current density dependent on the surface area of the work. However, it is difficult to measure and calculate the surface area of the work having a complicated shape. Accordingly, it is impossible to produce an accurate product having a high quality of lustrous surface.